1. Field of the Invention
The present invention relates to a wafer polishing machine. More specifically, the present invention relates to a pad-in template assembly which contacts a wafer during the final polishing process in the fabrication of silicon wafers for semiconductor devices.
2. Discussion of the Related Art
Wafers are generally used in the fabrication of semiconductor devices. A wafer is a circular plate formed by thinly slicing an ingot in which a silicon crystal as a semiconductor material is grown on the circumference thereof.
In the fabrication of silicon wafers for semiconductor devices, cylindrical silicon (ingot) is cut (sliced) into separate wafers. At this time, the surface of the cut wafer is protruded or grooved. Accordingly, polishing is required to planarize the wafers.
A wafer polishing machine comprises a surface plate, a mounting block, a polishing unit head, a central guide and a peripheral guide. While the polishing unit rotates, the wafer is polished via the interaction of a polishing cloth and a polishing solution provided on the surface plate.
At this time, pressurization of the polishing unit onto the wafer is as follows.
A wafer is provided on a wafer support member, e.g., template assembly and the wafer support member is adhered to the mounting block. While the polishing unit applies a predetermined pressure to the mounting block and rotates at the same time, it generates friction between the wafer and the polishing cloth and thus evenly polishes the surface of the wafer to produce a mirror finish.
The template assembly is used in the final wafer polishing process.
FIG. 1 is a view illustrating a conventional wafer support member. Hereinafter, the conventional wafer support member will be illustrated with reference to FIG. 1.
As mentioned above, the conventional wafer support member has a structure in which an epoxy glass 110 is laminated at the edge of a back material 120. Since a plurality of layers are laminated on the epoxy glass 110, the wafer support member serves as a retainer ring to guide and support such that the wafer is not separated from the head in the wafer polishing process.
However, the conventional wafer support member has the following problems.
FIG. 2A is a view illustrating the front surface of a polished wafer.
The front surface of the wafer is measured using an LLS measurement apparatus, SP2, after polishing. And, as shown in FIG. 2A, ARC typed fine scratches are present on the front surface of the wafer. The scratches are caused by fine glass fibers and foreign materials from the edge of the wafer support member.
FIG. 2B is a detailed view illustrating scratches present on the front surface of the wafer. As a result of detecting the front surface of the wafer using AFM, shallow scratches having a depth of 0.2 to 0.4 nm and a width of 300 to 600 nm were observed.